Printing ribbon feeding mechanism in a printer

ABSTRACT

Printing ribbon feeding mechanism in a printer having a pair of ribbon reel supporting shafts alternately driven in the opposite directions to each other so as to feed the printing ribbon from a reel supported on one of the shafts to a reel supported on the other shaft and vice versa. The feeding mechanism has a ratchet feeding member reciprocably moved between a pair of ratchet wheels secured to the shafts, respectively, each time the printing operation is effected, and swingable to alternately engage with either of the ratchet for driving the same, a detent member alternately engageable with either of the ratchet wheels so as to prevent the reverse rotation of the same, a compression spring connecting the ratchet feeding member to the detent member so that, when the ratchet feeding member engages with either one of the ratchet wheels, the detent member is also engaged with the ratchet wheel with which the ratchet feeding member engages, whereas, when the ratchet feeding member is swung to engage with the other ratchet wheel, the detent member is also swung to engage with the other ratchet wheel with which the ratchet feeding member engages, and a pair of detecting levers each adapted to detect the amount of the ribbon wound on the reel which is mounted on the respective shaft and cooperating with the ratchet feeding member so that, when the diameter of the coil of ribbon on either of the reels is reduced to a predetermined value, the detecting lever detecting the diameter reduced to the predetermined value engages with the ratchet feeding member so as to swing the same to disengage from the ratchet wheel with which it has been engaged and engage with the other ratchet wheel from which it has been disengaged thereby permitting the ribbon to be fed in the reverse direction. The reversing of the direction of feeding of the ribbon is automatically repeated during the printing operation of the printer.

United States Patent [191 Okabe Jan. 22, 1974 PRINTING RIBBON FEEDINGMECHANISM IN A PRINTER [75] Inventor: Katsuhiko Okabe, Tokorozawa,

Japan [73] Assignee: Kabushikikaisha Copal, ltabashi-ku,

Tokyo, Japan 221 Filed: Julyll, 1972 2] Appl. No.: 270,865

[30] Foreign Application Priority Data [58] Field of Search 197/151,160-165;

[56] References Cited UNITED STATES PATENTS 3,542,183 11/1970 Stiffler197/165 1,980,723 11/1934 Hartley.... 197/161 3,658,164 4/1972 Fujimoto197/165 3,037,448 6/1962 Blodgett et al. 197/165 X 1,937,145 ll/l933Gollwitzer 101/336 917,803 4/1909 Scott 197/160 1,309,403 7/1919 Fort197/160 Primary ExaminerRobert E. Pulfrey Assistant ExaminerR. T. RaderAttorney, Agent, or FirmKurt Kelman et al.

[5 7] ABSTRACT Printing ribbon feeding mechanism in a printer having apair of ribbon reel supporting shafts alternately driven in the oppositedirections to each other so as to feed the printing ribbon from a reelsupported on one of the shafts to a reel supported on the other shaftand vice versa. The feeding mechanism has a ratchet feeding memberreciprocably moved between a pair of ratchet wheels secured to theshafts, respectively, each time the printing operation is effected, andswingable to alternately engage with either of the ratchet for drivingthe same, a detent member alternately engageable with either of theratchet wheels so as to prevent the reverse rotation of the same, acompression spring connecting the ratchet feeding member to the detentmember so that, when the ratchet feeding member engages with either oneof the ratchet wheels, the detent member is also engaged with theratchet wheel with which the ratchet feeding member engages, whereas,when the ratchet feeding member is swung to engage with the otherratchet wheel, the detent member is also swung to engage with the otherratchet wheel with which the ratchet feeding member engages, and a pairof detecting levers each adapted to detect the amount of the ribbonwound on the reel which is mounted on the respective shaft andcooperating with the ratchet feeding member so that, when the diameterof the coil of ribbon on either of the reels is reduced to apredetermined value, the detecting lever detecting the diameter reducedto the predetermined value engages with the ratchet feeding member so asto swing the same to disengage from the ratchet wheel with which it hasbeen engaged and engage with the other ratchet wheel from which it hasbeen disengaged thereby permitting the ribbon to be fed in the reversedirection. The reversing of the direction of feeding of the ribbon isautomatically repeated during the printing operation of the printer.

4 Claims, 3 Drawing Figures PRINTING RIBBON FEEDING MECHANISM IN APRINTER BACKGROUND OF THE INVENTION The present invention relates to aprinting ribbon feeding mechanism in a printer.

Heretofore, a printing ribbon feeding mechanism has been proposed whichhas a pair of ribbon reel shafts adapted to be alternately driven in theopposite direction from each other so that the ribbon is fed from onereel mounted on a shaft to the other mounted on the other shaft untilthe length of the ribbon on the one reel is reduced to a predeterminedvalue, and then the direction of feeding of the ribbon is automaticallyreversed so as to unwind the ribbon from the other reel and wind thesame on the one reel until the length of the ribbon on the other reel isreduced to the predetermined value, the reversing of the feeding ofribbon being repeated during the operation of the printer.

However, the ribbon feeding mechanism of the prior art described aboveis very complicated in construction and requires a relatively largespace, thereby making the printer bulky and inaccurate in operation.

The present invention aims at avoiding the disadvantages of the priorart ribbon feeding mechanism as described above.

SUMMARY OF THE INVENTION The object of the present invention is toprovide a novel and useful printing ribbon feeding mechanism of the typedescribed above which avoids the disadvantages of the prior art ribbonfeeding mechanism and which is compact and simple in construction andaccurate in operation in alternately feeding the ribbon from one ribbonreel to the other reel and vice versa.

The above object is achieved in accordance with the present invention bythe provision of a printing ribbon feeding mechanism having a pair ofribbon reel supporting shafts each for mounting a ribbon reel thereonand provided with a ratchet wheel coaxially fixed thereto, which ischaracterized by a ratchet feeding member reciprocably driven betweenthe ratchet wheels each time the printing operation is effected andreciprocably swung in the opposite directions so as to be alternatelyengaged with either of the ratchet wheels for feeding the same, a detentmember swingably located between the ratchet wheels and alternatelyengageable with either of the ratchet wheels so as to prevent the samefrom rotating in the reverse direction to the feeding, a compressionspring swingably connecting the ratchet feeding member to the detentmember so that, when the ratchet feeding member is swung in onedirection to engage with one of the ratchet wheels, the detent member isswung by the action of the spring to engage with the one ratchet wheelengaged with the ratchet feeding member, whereas, when the ratchetfeeding member is swung in the opposite direction to engage with theother ratchet wheel, the detent member is swung to engage with the otherratchet wheel, and a pair of detecting levers each swingably supportedadjacent to and urged toward the respective reel supporting shaft so asto detect the diameter of the coil of ribbon wound on the reel mountedon the respective shaft, each of the detecting levers having anoperating arm for engaging with the ratchet feeding member when thediameter of the coil of ribbon detected thereby is reduced to apredetermined value thereby reversing the swinging of the ratchetfeeding member so that the direction of feeding of the ribbon isautomatically reversed.

By the construction of the feeding mechanism of the present inventiondescribed above, the ratchetfeeding member is coupled with the detentmember by a single compression spring thereby permitting the number ofparts for operating them to be extremely reduced so that the feedingmechanism is made very compact and simple in construction while theaccurate operation is insured.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view showing thegeneral construction of the ribbon feeding mechanism of the presentinvention;

FIG. 2 is a fragmentary perspective view showing the detecting levercooperating with a ribbon reel mounted on the ribbon reel mounting shaftof FIG. 1; and

FIG. 3 is a fragmentary perspective view showing the pawl or ratchetfeeding member and the detent member cooperating with the ratchet wheelof FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1,the printer incorporating the ribbon feeding mechanism of the presentinvention has a pair of parallel ribbon reel mounting shafts 1', 2'freely rotatably mounted in the printer at a relatively short distancefrom each other. Ribbon reels 1, 2 are detachably mounted on therespective shafts l, 2 so as to be rotated therewith. The shafts 1, 2are provided with ratchet wheels 3, 4 coaxially secured thereto,respectively.

A printing ribbon 16 wound on either one of the reels 1, 2 is lead tothe other of the reels over guide rollers R, R so that, when the otherof the reels is driven in one direction so as to wind the ribbon thereonwhile the one reel is left freely rotatable, the ribbon is unwound fromthe one reel and fed to the other reel over the guide rollers R, Rbetween which a non-illustrated printing mechanism of the printer isarranged so that the printing operation is effected thereby. When thelength of ribbon on the one reel is reduced to a predetermined value,the driving of the other reel is released and the one reel is driven inthe opposite direction so as to feed the ribbon in the reverse directionfrom the other reel to the one reel for winding the ribbon thereon. Thisoperation is repeated during the operation of the printer so as toalternately feed the ribbon from the one reel to the other and viceversa.

In order to alternately driving either of the shafts l, 2', a pawl orratchet feeding member 9 is located between the ratchet wheels 3, 4. Themember 9 is in the form of a general T-shape and is pivotally mounted onthe free end of an actuating lever 10 at a position intermediate the twoarms of the T-shape by a pivot shaft 10a and is provided with a pair ofabutments or ribbon feed reversing arms 9", 9" formed by the two arms ofthe T-shape the operation of which will be described later as well as apair of ratchet feeding claws 9', 9' formed at the free end of the stemof the T-shape.

The actuating lever 10 per se is swingably mounted in the printer at thecenter thereof by a pivot shaft 11 and is reciprocably swung by aconnecting lever 12 coupled with the printing mechanism and pivoted atthe other end of the lever by a pivot shaft 10b each time the printingoperation is effected. Thus, the ratchet feeding member 9 isreciprocably moved by the operation of the actuating lever 10 betweenthe ratchet wheels 3, 4 in the direction substantially perpendicular tothe line passing through the axes of the shafts 1', 2'. One of theratchet feeding claws 9' is engageable with the ratchet wheel 4 when themember 9 is swung in the direction D as shown in FIG. 1 so that theratchet wheel 4 is driven thereby during the operation of the actuatinglever 10, while the other ratchet feeding claw 9' is engageable with theratchet wheel 3 when the ratchet feeding member 9 is swung in theopposite direction as indicated by C.

A detent member 14 having detent claws 14' at the respective free endsthereof is pivotally supported in the printer adjacent to the ratchetfeeding claws 9', 9' between the ratchet wheels 3, 4 at its intermediateportion by a pivot shaft as shown. The detent claws 14' are alternatelyengageable with either of the ratchet wheels 3, 4 when the detent member14 is swung in either of the opposite directions so that the ratchetwheel engaged with the detent claw is prevented from rotating in thereverse direction to the feeding. The detent member 14 has a pivot shaft14a secured thereto at a position offset from the pivot point (15)toward the ratchet feeding member 9.

A coupling spring 13 is pivotally connected at its one end to the pivotshaft 140 while the other end is pivotally connected to a pivot shaft 9asecured to the ratchet feeding member 9 at the free end of the stem ofthe T- shape. Thus, the detent member 14 is swung by the action of thespring 13 to engage one of the detent claws 14 with the ratchet wheel 4when the ratchet feeding member 9 is swung in the direction D so as toengage one of the ratchet feeding claws 9' with the ratchet wheel 4,whereas, when the ratchet feeding member 9 is swung in the direction Cso as to engage the other of the ratchet feeding claws 9 with theratchet wheel 3, the detent member 14 is swung in the opposite directionby the action of the spring 13 so that the other of the detent claws 14is engaged with the ratchet wheel 3 while the ratchet wheel 4 isdisengaged from the detent member 14 to allow the free rotation of theratchet wheel 4.

A detecting lever 5 is pivotally supported in the printer adjacent tothe ratchet wheel 3 by a pivot shaft 6 as shown and is urged in theclockwise direction by a spring (not shown). The detecting lever 5 has adetecting arm 5' and an operating arm 5" integral therewith. Thedetecting arm 5 is adapted to contact with the coil of ribbon 16 woundon the reel I mounted on the shaft 1 and resiliently urged thereto bythe action of the spring urging the lever 5 so that the angular positionof the operating arm 5" is made to correspond to the diameter d of thecoil of ribbon 16 on the reel 1.

in like manner, another detecting lever 7 is pivotally mounted in theprinter by a shaft 8 adjacent to the ratchet wheel 4 and is urged towardthe same by a spring (not shown). The detecting lever 7 has a detectingarm 7' and an operating arm 7. The configuration and arrangement of thelever 7 with respect to the ratchet wheel 4 are in symmetrical relationto those of the lever 5 with respect to the ratchet wheel 3. Thus, theangular position of the operating arm 7" corresponds to the diameter dof the coil of ribbon wound on the reel 2 mounted on the shaft 2'.

Each of the operating arms 5", 7" is so shaped that it engages with therespective feed reversing arm 9" of the ratchet feeding member 9 duringthe operation of the actuating lever 10 when the diameter of the coil ofribbon detected by the detecting lever is reduced to a predeterminedvalue, so that the ratchet feeding member 9 is swung in the direction soas to be disengaged from the ratchet wheel which has been engagedtherewith and engaged with the ratchet wheel which has been disengagedtherefrom, thereby permitting the direction of feeding of the ribbon tobe reversed.

in operation starting from the initial condition, for example, whereinthe ratchet feeding member 9 and the detent member 14 are engaged withthe ratchet wheel 4 as shown in FIG. 1, the ratchet wheel 4 is driven inthe direction E by the ratchet feeding member 9 during the operation ofthe actuating lever 10 to feed the ribbon 16 from the reel 1 to the reel2 over the guide rollers R, R. Thus, the diameter d of the coil ofribbon on the reel 1 is being reduced while the diameter d of the coilof ribbon on the reel 2 is increased.

When the diameter d, of the coil of ribbon on the reel 1 detected by thedetecting lever 5 is reduced to a predetermined value for reversing thedirection of feeding of the ribbon, the operating arm 5" of the lever 5is swung toward the ratchet wheel 3 correspondingly to the reduceddiameter cl of the coil of ribbon so that the operating arm 5" isbrought into the path of movement of the feed reversing arm 9" of theratchet feeding member 9 during the operation of the actuating lever 10so as to be engaged with the feed reversing arm 9", thereby swinging theratchet feeding member 9 in the direction C so as to disengage theratchet feeding claw 9 from the ratchet wheel 4 and engage the ratchetfeeding claw 9 with the ratchet wheel 3, while, at the same time, thedetent claw 14' of the detent member 14 is disengaged from the ratchetwheel 4 and engaged with the ratchet wheel 3 by the action of the spring13. Therefore, the ratchet wheel 3 is driven in the direction F by theratchet feeding member 9 so as to feed the ribbon 16 from the reel 2 tothe reel 1 thereby reducing the diameter 41 of the coil of ribbon on thereel 2.

When the diameter d of the coil of ribbon on the reel 2 is reduced tothe predetermined value during the operation of the printer, theoperating arm 7" of the detecting lever 7 detecting the diameter d isbrought into the path of movement of the feeding reversing arm 9" of theratchet feeding member 9, so that the ratchet feeding member 9 is swungin the direction D so as to again engage the ratchet feeding claw 9' andthe detent claw 14' with the ratchet wheel 4 while the ratchet wheel 3is made freely rotatable by the disengagement thereof from the ratchetfeeding member 9 and the detent member 14.

The above described operation is repeated during the printing operationof the printer so as to alternately feed the ribbon from one reel to theother and vice versa.

I claim:

1. In a ribbon feeding mechanism having a pair of ribbon reel supportingshafts each adapted to mount thereon a printing ribbon reel and having aratchet wheel coaxially secured thereto, and means for alternatelydriving said shafts in respective opposite directions so as to wind aprinting ribbon onto the reel mounted on the driven shaft whileunwinding the ribbon from the reel mounted on the other shaft, whereinthe improvement comprises an actuating lever; means for swinging saidlever; a ratchet feeding member having two arms interposed between saidpair of ratchet wheels, a portion of said member intermediate said twoarms being pivotally mounted on said actuating lever in such a mannerthat said member is reciprocated between said ratchet wheels in adirection substantially perpendicular to a line passing through the axesof said shafts, said member having a pair of ratchet feeding claws oneof said claws engaging one of said ratchet wheels when said member ispivoted in one direction on said actuating lever while the other clawengages the other ratchet wheel when said member is swung in theopposite direction, said claws rotating the respective engaged wheelswhen said member is reciprocated; a detent member pivotally mountedbetween said ratchet wheels and having a pair of detent claws, one ofsaid detent claws being engaged with one of said ratchet wheels whensaid detent member is pivoted in one direction so as to prevent said oneratchet wheel from rotating in the direction opposite to the directionof rotation imparted by the associated ratchet feeding claw, while theother detent claw engages the other ratchet wheel when said detentmember is pivoted in the opposite direction; a compression spring havingrespective ends secured to said ratchet feeding member and to saiddetent member in such a manner that, when said ratchet feeding member ispivoted in a direction to engage said one ratchet feeding claw with saidone ratchet wheel, said detent member is pivoted by said spring in adirection to engage said one ratchet wheel with said one detent claw,whereas, when said ratchet feeding member is pivoted in the oppositedirection, said detent member is pivoted in the opposite direction bysaid spring; a pair of detecting levers pivotally mounted adjacentrespective ratchet wheels, each detecting lever having a detecting armengageable with a coil of printing ribbon wound on a reel mounted on theassociated shaft for detecting the diameter of the ribbon coil wound onthe reel, and an operating arm, whereby each operating arm is movedaccording to changes in the diameter of the coil of ribbon on theassociated reel, said operating arms respectively abutting against thearms of said ratchet feeding member during the reciprocating movement ofthe latter when the diameter of the associated coil of ribbon is reducedto a predetermined value as the coil of ribbon is unwound from the reel,and thereby pivoting said ratchet feeding member from the engagedratchet wheel to the other ratchet wheel whereby the ribbon feed isreversed.

2. A printing ribbon feeding mechanism comprising, in combination:

a. two shafts having respective axes;

b. a ribbon reel secured on each of said shafts for rotation about theaxis of the associated shaft and adapted to carry a portion of a ribbonin the form of a coil of ribbon wound on said reel;

c. two ratchet wheels respectively coaxially mounted on said shafts forjoint rotation with said reels;

d. a single pawl member movable between respective positions of drivingengagement with said wheels;

e. a single detent member movable between respective positions ofblocking engagement with said wheels;

f. coupling means coupling said pawl member and said detent member forsimultaneous movement between the respective positions thereof;

g. guide means for guiding said ribbon between said reels;

h. sensing means associated with each of said reels for sensing thediameter of the coil of ribbon on each of said reels, each sensing meansincluding 1. a sensing member pivotally mounted for engagement with acoil of ribbon wound on the associated reel, and for pivoting movementwhen the diameter of the engaged coil changes; i. operating meansconnected to each of said sensing means and responsive to said pivotingmovement when the diameter of said engaged coil reaches a predeterminedminimum value, for moving said pawl between said positions thereof, saidoperating means including an operating member fixedly fastened to saidsensing member for joint pivoting movement therewith, said operatingmember having an abutment portion; and j. drive means operativelyconnected to said pawl member for reciprocating the same in apredetermined path for thereby rotating each engaged wheel in apredetermined direction while said detent member blocks movement of saidengaged wheel in a direction opposite to said predetermined direction,said abutment portion of each operating means being located in said pathwhen the diameter of the coil engaged by the connected sensing meansreaches said predetermined minimum value. 3. A mechanism as set forth inclaim 2, wherein said coupling means include an elongated compressionspring having two end portions respectively secured to said pawl memberand to said detent member, said detent member being mounted for pivotingmovement between said positions thereof. I

4. A mechanism as set forth in claim 2, wherein said drive means includean actuating member, said pawl member being pivotally mounted on aportion of said actuating member for movement between said positionsthereof, and means for reciprocating said portion in said path.

1. In a ribbon feeding mechanism having a pair of ribbon reel supportingshaftS each adapted to mount thereon a printing ribbon reel and having aratchet wheel coaxially secured thereto, and means for alternatelydriving said shafts in respective opposite directions so as to wind aprinting ribbon onto the reel mounted on the driven shaft whileunwinding the ribbon from the reel mounted on the other shaft, whereinthe improvement comprises an actuating lever; means for swinging saidlever; a ratchet feeding member having two arms interposed between saidpair of ratchet wheels, a portion of said member intermediate said twoarms being pivotally mounted on said actuating lever in such a mannerthat said member is reciprocated between said ratchet wheels in adirection substantially perpendicular to a line passing through the axesof said shafts, said member having a pair of ratchet feeding claws oneof said claws engaging one of said ratchet wheels when said member ispivoted in one direction on said actuating lever while the other clawengages the other ratchet wheel when said member is swung in theopposite direction, said claws rotating the respective engaged wheelswhen said member is reciprocated; a detent member pivotally mountedbetween said ratchet wheels and having a pair of detent claws, one ofsaid detent claws being engaged with one of said ratchet wheels whensaid detent member is pivoted in one direction so as to prevent said oneratchet wheel from rotating in the direction opposite to the directionof rotation imparted by the associated ratchet feeding claw, while theother detent claw engages the other ratchet wheel when said detentmember is pivoted in the opposite direction; a compression spring havingrespective ends secured to said ratchet feeding member and to saiddetent member in such a manner that, when said ratchet feeding member ispivoted in a direction to engage said one ratchet feeding claw with saidone ratchet wheel, said detent member is pivoted by said spring in adirection to engage said one ratchet wheel with said one detent claw,whereas, when said ratchet feeding member is pivoted in the oppositedirection, said detent member is pivoted in the opposite direction bysaid spring; a pair of detecting levers pivotally mounted adjacentrespective ratchet wheels, each detecting lever having a detecting armengageable with a coil of printing ribbon wound on a reel mounted on theassociated shaft for detecting the diameter of the ribbon coil wound onthe reel, and an operating arm, whereby each operating arm is movedaccording to changes in the diameter of the coil of ribbon on theassociated reel, said operating arms respectively abutting against thearms of said ratchet feeding member during the reciprocating movement ofthe latter when the diameter of the associated coil of ribbon is reducedto a predetermined value as the coil of ribbon is unwound from the reel,and thereby pivoting said ratchet feeding member from the engagedratchet wheel to the other ratchet wheel whereby the ribbon feed isreversed.
 2. A printing ribbon feeding mechanism comprising, incombination: a. two shafts having respective axes; b. a ribbon reelsecured on each of said shafts for rotation about the axis of theassociated shaft and adapted to carry a portion of a ribbon in the formof a coil of ribbon wound on said reel; c. two ratchet wheelsrespectively coaxially mounted on said shafts for joint rotation withsaid reels; d. a single pawl member movable between respective positionsof driving engagement with said wheels; e. a single detent membermovable between respective positions of blocking engagement with saidwheels; f. coupling means coupling said pawl member and said detentmember for simultaneous movement between the respective positionsthereof; g. guide means for guiding said ribbon between said reels; h.sensing means associated with each of said reels for sensing thediameter of the coil of ribbon on each of said reels, each sensing meansincluding
 3. A mechanism as set forth in claim 2, wherein said couplingmeans include an elongated compression spring having two end portionsrespectively secured to said pawl member and to said detent member, saiddetent member being mounted for pivoting movement between said positionsthereof.
 4. A mechanism as set forth in claim 2, wherein said drivemeans include an actuating member, said pawl member being pivotallymounted on a portion of said actuating member for movement between saidpositions thereof, and means for reciprocating said portion in saidpath.